Hydralazine for Hypertension Treatment

While hydralazine has been largely replaced by other drugs for the treatment of high blood pressure, it still plays an important role in certain types of patients, especially patients with newly diagnosed gestational hypertension, and those with severely elevated high blood pressure that does not respond well to other therapies. Hydralazine can be administered in several different ways, making it well suited to situations requiring flexibility in dosing.

Person taking high blood pressure medication with box of pills and a glass of water on a white table
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How Hydralazine Works

Hydralazine works by causing the muscles which line and surrounding arteries to relax, resulting in dilation and lowered blood pressure. While the precise details of how hydralazine causes this relaxation are not known, it is believed that hydralazine interferes with the transfer of calcium inside of muscle cells. Since muscles cannot contract without calcium, this interference results in muscle relaxation. Along with this relaxation, hydralazine also causes an increase in heart rate and an increase in the total amount of blood being pumped by the heart.

Other Drugs like Hydralazine

Hydralazine is formally known as a direct-acting vasodilator, which means that it works directly on the blood vessels themselves to cause relaxation. While there are many different types of vasodilators used in medicine today, none share the chemical or clinical properties of hydralazine. Hydralazine is the only drug of its kind currently used in the United States and is not a member of a larger, clinically relevant class of compounds. Though typically dispensed as a generic drug, hydralazine may sometimes still be found at the brand name drug Apresoline.

Side Effects of Hydralazine

Hydralazine tends to increase heart rate and may cause fluid retention through its action on the kidneys.These effects are usually countered by giving hydralazine along with other medicines like beta-blockers and diuretics, though this is not always possible in pregnant patients. Some common side effects of hydralazine include:

  • Headache
  • Nausea
  • Decreased appetite
  • Diarrhea

Rarely, hydralazine may cause a serious disease known as drug-induced systemic lupus erythematosus, which causes the immune system to attack normal cells. This condition almost always resolves once the hydralazine is stopped.

Notes About Hydralazine

Only you and your healthcare provider can decide on a proper medication for the treatment of high blood pressure. Be sure to notify your healthcare provider if you are pregnant or breastfeeding, and to supply the names of any other medicines and/or supplements you are taking. Remember to include over-the-counter medicines, like aspirin or Advil (ibuprofen), and herbal/natural supplements.

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2 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Bang L, Nielsen-kudsk JE, Gruhn N, et al. Hydralazine-induced vasodilation involves opening of high conductance Ca2+-activated K+ channels. Eur J Pharmacol. 1998;361(1):43-9. doi:10.1016/s0014-2999(98)00701-8

  2. Messerli FH. Vasodilatory edema: a common side effect of antihypertensive therapy. Curr Cardiol Rep. 2002;4(6):479-82. doi:10.1007/s11886-002-0110-9

Additional Reading
  • Sources:
  • Hydralazine Hydrochloride. (n.d.). DRUGDEX® System Retrieved December 4, 2007, from http://www.thomsonhc.com. Greenwood Village, CO: Thomson Healthcare.